1. Field of the Invention
The present invention relates to an air-cooled type laser device having a laser diode as a light emitting source or an excitation light source, and having a structure for radiating heat generated from the laser diode.
2. Description of the Related Art
Generally, in a laser device, having a laser diodes (or semiconductor lasers) as a light emitting source or an excitation light source, there are two types, i.e., an air-cooled type in which heat generated by a laser diode module including a laser diode is radiated by air; and a water-cooled type which is connected to a circulation type cooling water supply device (or a chiller).
The air-cooled type laser device is more advantageous than the water-cooled type, in that the air-cooled type is easily moved, an occupied area thereof is small, restrictions of an installation location thereof are few, and an installation cost thereof is low, etc. However, in the air-cooled type, it is difficult to decrease the temperature of the laser diode module to the same degree of the water-cooled type. In particular, since a high-power laser device must have many laser diode modules having a large amount of heat generation, it is necessary to provide an effective heat radiating structure to the laser device in order to prevent the laser device from having to be increased in size.
As a relevant prior art document, JP 2008-021899 A discloses a laser oscillator having a semiconductor laser heat radiating member to radiate heat generated by a semiconductor laser array, a fiber laser heat radiating member to radiate heat generated by an optical fiber for a fiber laser, a cooling fan for sending cooling air, and a guide member for guiding the cooling air from the cooling fan.
JP 2012-059952 A discloses a structure for cooling an electronic device, including a heat radiator having an L-shaped heat pipe, a plurality of heat radiating fins attached to a substantially horizontal part of the heat pipe, and a heat receiving plate to which substantially vertical portions of the heat radiating fins are attached; a plurality of electronic devices attached to the heat receiving plate; and a container for containing the plurality of electronic devices.
JP 2009-239166 A discloses a flat heat sink including: a plurality of thin plates layered having an air guiding portion and a hollow portion for containing a centrifugal fan, the thin plated being layered with a certain gap therebetween; at least one heat radiating fin part connected to ends of the thin plates, in which air guided by the air guiding portion of the thin plates flows through the heat radiating fin part; and at least one heat pipe, having one end which is thermally connected to the portion of the thin plate thermally connected to a heating component and the other end which is thermally connected to the heat radiating fin part, in which at least a part of the heat pipe is positioned so as to form a space between the thin plates and the heat pipe.
Further, WO 2014/092057 A1 discloses a cooling unit having a heat receiving block thermally connected to an electronic component constituting a heating element, a heat pipe vertically positioned on the heat-receiving block and configured to receive and transfer heat of the heat-receiving block, and a plurality of heat radiating fins arranged on the heat pipe. The heat radiating fins are constituted by a first fin set arranged on a linear portion of the heat pipe and a second fin set arranged on a bent portion of the heat pipe.
In an open-type air-cooled laser device, in which external air is sucked as cooling air into the laser device, and the air heated by a laser diode in the laser device is discharged from the laser device, when the outside air temperature (or the ambient temperature) of the laser device is increased, the temperature of the air sucked into the laser device is also increased, whereby it is difficult to effectively cool the laser diode. Therefore, in order to extend a life of the laser diode module and improve reliability thereof, a panel cooler may be used so as to cool the air within a housing (or the laser device) having a substantially sealing structure, and a heat radiating fin set may be cooled by the cooled air, in which the fin set is thermally connected to a heat-receiving member which receives heat from the laser diode.
However, in a laser device having a high optical output (i.e., having a laser diode module with a large amount of heat generation), it is necessary to arrange a large fin set (in particular, having a large inflow area) in the laser device in order to sufficiently lower the temperature of the heat-receiving member, whereby the housing (or the laser device) may be increased in size.
The above related art documents do not provide a sufficient solution for solving the above problems. For example, although an open-type air-cooled laser oscillator is disclosed in FIG. 5 of JP 2008-021899 A, it is necessary to reflux the air discharged from an outlet port into an inlet port again and arrange a flow path therefor, when the laser oscillator is positioned in a housing having a substantially sealing structure. Further, in order to obtain high cooling characteristics, it is necessary to circulate a large amount of air at a high velocity. Accordingly, it is necessary to increase a cross sectional area of the flow path, whereby the device is increased in size. When the device is increased in size, an installation area and a weight thereof are also increased. Further, due to increase in a surface area of the device, a heat input from the outside to the device is also increased, whereby it is necessary to use a panel cooler having high cooling capability, by which a device cost and an operation cost thereof are increased.